It looks like the final specifications for both the NVIDIA GeForce GTX 750 Ti and GTX 750 have been revealed by Vietnamese site Tinhte.vn. The information is directly from an NVIDIA press conference where NVIDIA was going over the Maxwell architecture and the new cards.
NVIDIA GeForce GTX 750 Ti
The GeForce GTX 750 Ti will make use of the full GM107 GPU, so it will have 640 CUDA cores, 40 TMUs and 16 ROPs. There will be 2 GB of GDDR5 running across a 128-bit interface. The memory will be clocked at 5400 MHz (effective). The official TDP for the card is 60W. It will be clocked at 1020 MHz core and 1085 boost. The card does support GPU Boost 2.0.
NVIDIA GeForce GTX 750
The GeForce GTX 750 (Non Ti version) will have 512 CUDA cores, 32 TMUs, and 16 ROPs. It will have 1 GB of memory that also runs across a 128-bit interface. The memory will be clocked lower than the GTX 750 Ti and will be set at 5.0 GHz (effective). The official TDP is 55W. The card will have the same clocks as the GTX 750 Ti.
You will not need a power connector for either card.
The guys over at VideoCardz made a nice graph of the cards and the card that they will replace, which is the GeForce GTX 650 Ti.
And here are some more shots of the card…
And the actual slides from the press conference that confirm the specifications and go over the Maxwell architecture.